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Research Library

TNR results: Free-roaming cat numbers reduced in rural study


“Analyzing approaches to feral cat management — one size does not fit all,” published in the Journal of the American Veterinary Medical Association, 2004. Complete article available online here.


In pilot studies related to a long-term study of a trap-neuter-return (TNR) program in rural North Carolina [1], researchers documented a 36% average population reduction across six colonies of sterilized cats during the first two years. Meanwhile, the population of three unsterilized colonies (serving as “controls”) increased by an average of 47% [2].

Key points

Researchers reported population reductions across the six colonies of sterilized cats, with each colony reduced to 30–89% of its original size after two years.

"Researchers documented a 36% average population reduction across six colonies of sterilized cats during the first two years."

Population increases in the three unsterilized colonies, on the other hand, varied considerably: one had been reduced to 31% of its original size while the others increased to 127% and 283% of original size. (Details regarding the specific number of cats in each colony were not provided in the published paper.)

The population reductions reported here are consistent with those reported by other researchers investigating the effectiveness of targeted TNR efforts [3–8].

As the paper’s title suggests, the authors emphasize the point that “different solutions will fit different situations.” Where management strategies are particularly contentious, clear goals must be established (e.g., a specific reduction in cat numbers over a specified period of time) and strategies agreed upon “by analytically examining the perceived risks of management options as held by all interested parties.”



  1. Nutter, F.B. Evaluation of a Trap-Neuter-Return Management Program for Feral Cat Colonies: Population Dynamics, Home Ranges, and Potentially Zoonotic Diseases, North Carolina State University: Raleigh, NC, 2005.

  2. Stoskopf, M.K.; Nutter, F.B. Analyzing approaches to feral cat management—one size does not fit all. Journal of the American Veterinary Medical Association 2004, 225, 1361–1364.

  3. Levy, J.K.; Gale, D.W.; Gale, L.A. Evaluation of the effect of a long-term trap-neuter-return and adoption program on a free-roaming cat population. Journal of the American Veterinary Medical Association 2003, 222, 42–46.

  4. Spehar, D.D.; Wolf, P.J. An Examination of an Iconic Trap-Neuter-Return Program: The Newburyport, Massachusetts Case Study. Animals 2017, 7.

  5. Spehar, D.D.; Wolf, P.J. A Case Study in Citizen Science: The Effectiveness of a Trap-Neuter-Return Program in a Chicago Neighborhood. Animals 2018, 7.

  6. Swarbrick, H.; Rand, J. Application of a Protocol Based on Trap-Neuter-Return (TNR) to Manage Unowned Urban Cats on an Australian University Campus. Animals 2018, 8.

  7. Kreisler, R.E.; Cornell, H.N.; Levy, J.K. Decrease in Population and Increase in Welfare of Community Cats in a Twenty-Three Year Trap-Neuter-Return Program in Key Largo, FL: The ORCAT Program. Frontiers in Veterinary Science 2019, 6.

  8. Spehar, D.D.; Wolf, P.J. Back to School: An Updated Evaluation of the Effectiveness of a Long-Term Trap-Neuter-Return Program on a University’s Free-Roaming Cat Population. Animals 2019, 9.


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